Fumigant mixture



. According to the present Patented July 20,

- UNITED" STATE PATENT OF Flclz FUMIGANT mx'rn ta William w. Allen and MW. Fletcher, Midland,

MlclL, assignors to The Dow Chemical Com Michigan Q No Drawing. Application October 17,

Serial No. 415,409

3 Claims. (Cl. 99-225) limited to a particular type of-fumigation procedure.

With increased inventories of surplus grains,- the control of weevils and related insect pests has become a problem ofmaior importance. The stored grain is generally held in bins or granaiies forperiods running from one season to several years and frequently become so badly infested with weevils, beetles, and the like as to be 0 little value for human consumption.

Much time and money has been expended by both governmental and private agencies in an *eifort to evolve control methods for grain infest:

ing insects. The amounts of many of th known fumigants required to accomplish such control are so large that the cost of treatment is prohibitive. Furthermore, the controls obtained with such toxicants are frequently erratic and unsatisfactory even at relatively high concentrations due to variations in stored grain tempera tures, and problems of-penetratlon, vapor distribution, and channeling.

fumigant mixtures are provided which comprise as a major toxic ingredient a methylene chloride mixture 0 containing a substantial amount of methyl bromide. The expression "substantial amoun as herein employed refers to from about 3 to about 50 per cent by weight. In view of the disparity between the densities of methylene chloride and methyl bromide, on a volume basis the methylene chloride predominates in such mixtures. These new fumisants havebeen found superior with respect to their control of grain invention, improved Midland, Mich, a corporation of further advantage resides in such compositions the use of high pressure containers and special applicators as required with a methyl bromide alone is avoided to som extent by the lowering of the vapor pressure and reduction in rates of vaporization attributable to the large proportions of methylene chloride employed. While reasonable precautions are still required, it is frequently possible to avoid the use ofthick walled cylinders and the like as contain ers for the new'mixtures.

The invention also provides a procedure whereby grain stored in bins is treated with the new methylene chloride-methyl bromide mixtures to obtain an economical and eflicient control of weevils, borers, and beetles. This procedure comprises introducing the fumigant' mixture at the top of a filled bin, granary, elevator, etc. and onto 1 the surface of the grain. The vapor pressures of the new mixtures are such that a gradual distribution and penetration of the toxic vapor occurs throughout the limits of the confining structure with the substantial absence of the undesirable channelling effect ordinarily observed with methyl bromide and the localized control inherent-to methylene chloride.

, The amounts of the new compositions required to accomplish control of insects at all levels of the stored grain are relatively small and it appears that aneffect is exerted by, the mixture of toxicants which is much greater than the sum of the toxicities of the constituents. Thus from about 1 to about 3 gallons of the methylene chloride-methyl bromide mixture per 1000 bushels of grain give commercial control of insect pests. Whenused alone, amounts of each constituent in excess of those required in the mixture frequently are not satisfactory.

The following table sets forth the results obtained oncom with a representative methylene chloride-methyl bromide mixture and with methylene chloride and methyl bromide alone. The organism concerned was Tribolium conjusum, i. e.

parasites, particularly in bin fumigations. A 4 the confused flour beetle.

Table l Per cent control at V?fl 0lll levels below- Fumigant Lbs. 00

material bushels Surface 1.1m. am. 4.51:. am. am.

gggm ff 3: 22.6 100 100 100 100 10c Methyienechl de. 1 22.1 i 14 c5 79 7o 36 14 Methyl bromide... 5 1o 0 s s 2 100 the fact that with.

.In carrying out the fumigations which resulted in the foregoing data, cages-containing a dell.

- nite number of'test insects were introduced into a bin at th surface of and at different levels in the 'stored corn. The i'umigants were applied at 'the top of the bin by sprinkling on the surface of the grain. Each bin was thereafter closed and allowed to stand for three days. Thecages were 4 then removed from the several levels and the 'degree of control calculated on the basis of observed insect mortality. I

The foregoing compositions are efiective not I only against the confused flour beetle but also methyl bromide mixture or as added 'tnxicants.

Representative of such materials are ethylene chloride, trichloro ethylene, ethylene ehlorobromide, propylene ehlorobromide, chloroform, chloropicrin, ethylene oxide, etc.

We claim:

1. In a method for fumigating insect" infested grain stored in bins the step of introducing 0. volatile fumigantcomprising as a maior toxic ingredient a. mixture or methylene chloride with s substantialpmportion of methyl bromide in the top of the bin and onto the surface of the stored grain.

2.- A volatile liquid fumigant comprising a mixture of methylene chloride with a substantial proportion of methyl bromide.

3. A volatile liquid fumisant comprising as s major toxic ingredient a mixture of methylene chloride with a substantial proportion of methyl bromide. I v WILLIAM W. ALLEN. FRED W. FLETCHER. 

